User Suggested edit - workaround for preserving tabs

Markedjs by default changes leading tabs to spaces. More details:
markedjs/marked#1559

As workaround we extract user suggestion from content of
gr-formatted-text which has tabs and not spaces.

Release-Notes: skip
Google-Bug-Id: b/279925682
Change-Id: I0a6d0223b384838b29753c41437b9174dda0da46
(cherry picked from commit a37ffe3)

polygerrit-ui/app/elements/shared/gr-formatted-text/gr-formatted-text.ts

@@ -21,7 +21,10 @@ import '../gr-account-chip/gr-account-chip';
 import '../gr-user-suggestion-fix/gr-user-suggestion-fix';
 import {KnownExperimentId} from '../../../services/flags/flags';
 import {getAppContext} from '../../../services/app-context';
-import {USER_SUGGESTION_INFO_STRING} from '../../../utils/comment-util';
+import {
+  getUserSuggestionFromString,
+  USER_SUGGESTION_INFO_STRING,
+} from '../../../utils/comment-util';
 
 /**
  * This element optionally renders markdown and also applies some regex
@@ -298,9 +301,16 @@ export class GrFormattedText extends LitElement {
   }
 
   private convertCodeToSuggestions() {
-    for (const userSuggestionMark of this.renderRoot.querySelectorAll('mark')) {
+    const marks = this.renderRoot.querySelectorAll('mark');
+    if (marks.length > 0) {
+      const userSuggestionMark = marks[0];
       const userSuggestion = document.createElement('gr-user-suggestion-fix');
-      userSuggestion.textContent = userSuggestionMark.textContent ?? '';
+      // Temporary workaround for bug - tabs replacement
+      if (this.content.includes('\t')) {
+        userSuggestion.textContent = getUserSuggestionFromString(this.content);
+      } else {
+        userSuggestion.textContent = userSuggestionMark.textContent ?? '';
+      }
       userSuggestionMark.parentNode?.replaceChild(
         userSuggestion,
         userSuggestionMark

polygerrit-ui/app/utils/comment-util.ts

@@ -476,13 +476,17 @@ export function hasUserSuggestion(comment: Comment) {
   return comment.message?.includes(USER_SUGGESTION_START_PATTERN) ?? false;
 }
 
-export function getUserSuggestion(comment: Comment) {
-  if (!comment.message) return;
+export function getUserSuggestionFromString(content: string) {
   const start =
-    comment.message.indexOf(USER_SUGGESTION_START_PATTERN) +
+    content.indexOf(USER_SUGGESTION_START_PATTERN) +
     USER_SUGGESTION_START_PATTERN.length;
-  const end = comment.message.indexOf('\n```', start);
-  return comment.message.substring(start, end);
+  const end = content.indexOf('\n```', start);
+  return content.substring(start, end);
+}
+
+export function getUserSuggestion(comment: Comment) {
+  if (!comment.message) return;
+  return getUserSuggestionFromString(comment.message);
 }
 
 export function getContentInCommentRange(